Fe-Rich Ni_0.06Fe_0.94OOH Nanorods as Efficient Electrocatalysts for the Oxygen Evolution Reaction

Abstract

Developing Fe-rich oxygen evolution reaction (OER) electrocatalysts has remained a challenge due to the structural rigidity of the phases. However, wide distribution of the Fe source around the globe and inexpensiveness compared to other transition metals (Ni, Co, etc.) make their development a priority in electrocatalysis research. Herein, we report the synthesis of a Fe-rich OER electrocatalyst (Ni 0.06 Fe 0.94 OOH) that operates at significantly higher efficiency compared to Nirich materials. A controlled synthesis using polyethylenimine as a capping agent was adapted, which rendered FeOOH nanorods with excellent colloidal stability. Incorporation of a minuscule amount (6%) of Ni(II) in the material resulted in the dramatic enhancement of geometric OER activity compared to Ni-rich phases. The Ni 0.06 Fe 0.94 OOH catalyst possesses a low overpotential of 287 ± 9 mV compared to FeOOH, which required 495 ± 8 mV to reach the benchmark current density of 10 mA/cm 2 . The catalyst displayed a low Tafel slope of 69 mV/dec and high selectivity with a Faradaic efficiency of 92%. The catalyst was stable for 2000 cycles of CV performed at a scan rate 10 mV/s, and a steady potential response was generated for 24 h at a 100 mA/cm 2 current density.

Efficient Electrochemical Reconstruction of a Cobalt- and Silver-Based Precatalytic Oxalate Framework for Boosting the Alkaline Water Oxidation Performance

“…The ρRHE value is found to be 0.8, elucidating the OOH (ads) + OH – → OO (ads) + H 2 O + e – mechanism that is predominantly known as a driving force for the PDET step (Figure b). , However, the ρRHE value is found to be 0.71 for the pristine CoC 2 O 4 sample, revealing a lower pH dependence compared to that of CoC 2 O 4 /Ag 2 C 2 O 4 (Figure S22). Correlating our observation with previous reports shows that promoting the PDET mechanism just using a minimal amount of silver inclusion can trigger the OER performance through more number of *OH or *OOH sites that could bring rapid kinetics and lower charge-transfer resistance for alkaline OER. , As mentioned in the Introduction, one of the challenges in the silver-doped electrocatalytic materials for OER is their stability. To evaluate the long-term stability, CoC 2 O 4 /Ag 2 C 2 O 4 was subjected to a 24 h stability experiment using the chronopotentiometry method (Figure c).…”

“…71,72 However, the ρRHE value is found to be 0.71 for the pristine CoC 2 O 4 sample, revealing a lower pH dependence compared to that of CoC 2 O 4 /Ag 2 C 2 O 4 (Figure S22). 73 Correlating our observation with previous reports shows that promoting the PDET mechanism just using a minimal amount of silver inclusion can trigger the OER performance through more number of *OH or *OOH sites that could bring rapid kinetics and lower charge-transfer resistance for alkaline OER. 37,74 As mentioned in the Introduction, one of the challenges in the silver-doped electrocatalytic materials for OER is their stability.…”

Approach to Evaluation of Electrocatalytic Water Splitting Parameters, Reflecting Intrinsic Activity: Toward the Right Pathway

“…Because of the restrictions associated with determining the ECSA, researchers have recently employed the BET surface area to normalize the activity and obtain the specific activity. They demonstrated that current is normalized by BET surface area ( j BET ) which is typically employed for powder electrocatalysts [26d] . The BET surface areas of materials were determined by the amount of N 2 gas absorbed and desorption measurements from them (in some cases, CO, O 2 , H 2 , and other gases were also used) [32,33] .…”

Design of a High-Efficiency Bifunctional Electrocatalyst: Rich-Nitrogen-Doped Reduced Graphene Oxide-Modified Carbon Cloth-Growing Nickel–Iron Complex Oxides for Overall Water Splitting

“…6,7 To solve the above problems, Ni−Fe-based bimetallic nanoparticles and composite hybrid nanocatalysts with high electrocatalytic activities were constructed in the past few years. 33 For example, Koppisetti's group 34 synthesized an Fe-rich OER electrocatalyst (Ni 0.06 Fe 0.94 OOH) that operated at a low overpotential of 287 mV compared with FeOOH to provide the benchmark current density of 10 mA•cm −2 . The electrocatalyst also possessed a low Tafel slope of 69 mV•dec −1 and a high selectivity with 92% Faradaic efficiency, which was significantly higher compared with Ni-rich materials.…”

“…For example, Koppisetti’s group synthesized an Fe-rich OER electrocatalyst (Ni 0.06 Fe 0.94 OOH) that operated at a low overpotential of 287 mV compared with FeOOH to provide the benchmark current density of 10 mA·cm –2 . The electrocatalyst also possessed a low Tafel slope of 69 mV·dec –1 and a high selectivity with 92% Faradaic efficiency, which was significantly higher compared with Ni-rich materials.…”